The present invention relates to wireless communication technology, and more particularly, to a wireless sensor network having an upper node that periodically transmits a beacon message and at least one lower node that communicates with the upper node in response to the received beacon message.
In general, wireless sensor network technology is classified into wireless local area network (WLAN) technology and wireless personal area network (WPAN) technology according to the recognition distance thereof. WLAN is based on IEEE 802.11 and enables devices to be connected to a backbone network within a radius of 100 m. On the other hand, WPAN is based on IEEE 802.15 and includes Bluetooth, Zigbee, and ultra wide band (UWB), and is used over a more limited range. Wireless sensor networks, in which wireless sensor network technology is established, are configured to include an upper node and lower nodes. The upper node and lower nodes are each operated by battery power.
In such a wireless sensor network, the upper node and lower nodes are permitted to communicate with each other only in a predetermined active interval in order to reduce power consumption. The upper node can transmit data to the lower nodes in the active interval. Since the lower nodes request data from the upper node based on competition-based channel linking, the efficiency of data transmission deteriorates from the upper node to the lower nodes. Therefore, the upper node and the lower nodes waste battery power. This problem worsens as the number of lower nodes communicating with the upper node increases.